The hydroformylation of oxiranes to produce 3-hydroxyaldehydes has been discussed in “New Syntheses with Carbon Monoxide” edited by J. Falbe (1980), pp. 131-132. The reaction is catalyzed with a cobalt-based catalyst, or a phosphine-modified cobalt-based catalyst. The hydroformylation product, be it the 3-hydroxyaldehyde or the cyclic hemiacetal (its dimer) may be converted into a 1,3-alkanediol by hydrogenation. This process is of particular importance to the preparation of 1,3-propanediol (PDO), an intermediate in the production of polytrimethylene terephthalate for fibers and films, that may be prepared by hydrogenating 3-hydroxypropanal (HPA).
U.S. Pat. No. 5,463,145 describes a process for producing the hydroformylation product at improved rates. The process utilizes water as the extraction solvent, cobalt in the catalyst and a promoter which is a lipophilic quaternary salt of a Group V element. The catalyst and promoter are conveniently recycled with the organic phase which readily separates from the water extraction solvent and is then recycled to the hydroformylation stage. Unfortunately, water has a high heat of vaporization which makes the cost of separating water from the 1,3-alkanediol product in this process considerably higher than such cost in conventional petrochemical processes which use solvents with lower heats of vaporization. Also, the water must be purified to be recycled to the extraction stage because the presence of PDO can cause loss of the hydroformylation catalyst and/or the promoter and the presence of light ends such as ethanol can cause other problems with the hydroformylation catalyst and/or the promoter.
It would be advantageous to reduce the energy required to separate the excess water and find a way to reuse the water in the extraction stage without expensive purification.